Aspects and embodiments of the invention most generally pertain to an optical component capable of manipulating a light input in a desired manner; more particularly to an optical circulator and, most particularly to a monolithically integrated semiconductor optical circulator with multiple optical ports that is capable of routing optical pulses directionally from port to port with better than 20 dB of isolation for the flow of optical pulses in the reverse direction, associated methods, and applications.
The integration of critical optical components on a single chip has been an ongoing quest in both optoelectronics and optical communication systems. Among the possible devices, elements supporting non-reciprocal transmission are of great interest for applications where signal routing and isolation is required. In this regard, breaking reciprocity is typically accomplished via Faraday rotation through appropriate magneto-optical arrangements. Unfortunately, standard light emitting optoelectronic materials, for example III-V semiconductors, lack magneto-optical properties and hence cannot be directly used in this capacity. To address these issues, a number of different tactics have been attempted in the last few years. These range from directly bonding garnets on chip, to parametric structures and unidirectional nonlinear arrangements involving ring resonators.
Optical circulators—devices capable of routing signals in a unidirectional fashion between their successive ports—play a crucial role in photonic networks. Such non-reciprocal devices typically involve magneto-optical garnets in conjunction with permanent magnets to provide isolation. However, in most photonic on-chip settings the bonding of garnets and the integration of magnets, though possible, is not readily conducive. In addition, these arrangements either the trade-off between a large foot-print and device bandwidth. Moreover, these approaches, due to the excessive losses, have provided only a limited degree of isolation.
In view of the foregoing and other shortcomings recognized by those skilled in the art, the inventors have recognized the benefits and advantages of enabled non-reciprocal devises that not only can be miniaturized and readily integrated on chip but that also rely on physical processes that are indigenous to the semiconductor wafer itself. According to the embodied invention, such unidirectional systems can be implemented by simultaneously exploiting the presence of gain/loss processes and optical nonlinearities. In principle, these all-dielectric structures can be broadband, polarization insensitive, color-preserving, and can display appreciable isolation ratios under pulsed conditions.